Portland's police chief on Sunday acknowledged allegations of injuries suffered a day earlier as officers cleared streets and fired various crowd-control munitions near crowds of protesters.

Chief Danielle Outlaw said any complaints would be forwarded to the Office of Independent Police Review.

"This morning I learned of allegations of injury as a result of law enforcement action," Outlaw said in a statement. "I take all force applications by members seriously and I have directed the Professional Standards Division to begin the intake process regarding these allegations to determine if force was used and if so, was within our policy and training guidelines."

Reports of injuries appeared on social media during and after the demonstrations. Some were widely shared, but could not be independently confirmed.

The police bureau said Saturday that three people were treated by Portland Fire medics, and one was taken by ambulance to a local hospital with a non-life-threatening injury. None of those injuries were the result of police actions, police spokesman Sgt. Chris Burley said.

Police officers are required to write reports after using force, the bureau said, and the bureau said it reviews those reports to determine if the actions were within its policies.

The statement said complaints about officer conduct could be sent directly to the Office of Independent Police Review for investigation through an online form or by calling (503) 823-0146.

Police were stationed in large numbers in downtown Portland on Saturday in anticipation of a face-off between the right-wing group Patriot Prayer and groups of counter-protesters. Police lined Southwest Naito Parkway in an effort to keep the groups separated.

Around 2 p.m., officers ordered a group of counter-protesters near the intersection of Southwest Naito Parkway and Southwest Columbia Street to disperse. When the group didn't immediately leave, police fired dozens of flash-bang grenades other crowd-control munitions. Officers rushed toward the crowd, shoving some protesters out of the street.

Police said protesters had thrown a "chemical agent" and other objects at officers.

An object thrown at police after the dispersal order was given hit Eder Campuzano, a reporter from The Oregonian/OregonLive, in the head. He was bloodied, but is doing fine.

KATU-TV photojournalist Ric Peavyhouse reported he visited a doctor after being hit by one of the "less lethal impact rounds" police used Saturday. Peavyhouse said the doctor instructed him to "just take it easy" as he recovers from his injury.

The runup to the demonstration took on an ominous tone after Gibson moved it to Tom McCall Waterfront Park, where those with permits to carry concealed weapons could legally arm themselves. Gibson also encouraged his supporters, who were legally able, to bring guns to the protest.

Throughout the day, Portland police released images of weapons collected from both sides, including knives, sticks, shields and fireworks. Unlike past demonstrations, however, Saturday's dueling events never turned into the melee that many had predicted.

The bureau said earlier it had made four arrests during Saturday's events:

Robert J. Majure, 27, on suspicion of harassment and resist arrest;

Tracy L Molina, 45, on suspicion of second-degree disorderly conduct and attempted assault on a public safety officer;